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231.
P. T. Jochym K. Parlinski A. M. Oleś 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,61(2):173-179
The magnetization distribution, its energetic characterization by the
interlayer coupling constants and lattice dynamics of (001)-oriented
Fe/Pt multilayers are investigated using density functional theory
combined with the direct method to determine phonon frequencies.
It is found that ferromagnetic order between consecutive Fe layers is
favoured, with the enhanced magnetic moments at the
interface. The bilinear and biquadratic coupling coefficients between Fe
layers are shown to saturate fast with increasing thickness of
nonmagnetic Pt layers which separate them. The phonon calculations
demonstrate a rather strong dependence of partial iron phonon
densities of states on the actual position of Fe monolayer
in the multilayer structure. 相似文献
232.
Pd80+x
Si20−x
(x = 0, 1, and 2) binary metallic glasses with the diameter ranging from 7 to 8 mm were prepared by a combination of fluxing
and water quenching or air cooling. Thermal analysis results show that with increasing Si content, the glass transition temperature
T
g, the initial crystallization temperature T
x and the onset crystallization temperature T
p of Pd-Si binary glassy alloys increase. Moreover, the supercooled liquid region reaches 61 K. It indicates that Pd-Si binary
alloys possess large glass forming ability, which can be greatly improved by fluxing treatment.
Supported by the National Basic Research Program of China (Grant No. 2007CB613905) and the National Natural Science Foundation
of China (Grant Nos. 50671050 and 50431030) 相似文献
233.
The thermodynamics structural relaxation of Fe73Cu1.5Nd3Si13.5B9 amorphous alloy from room temperature to 400°C has been investigated by measuring the structure factor with in situ X-ray diffraction. The structural information of the atomic configuration such as radial distribution function (RDF) and
neighbor atomic distance was gained by Fourier transformation. The research result shows that the amorphous structure remains
stable in the temperature range of 30 to 400°C but exhibits distinct changes in local atomic configuration with the increase
of temperature. The quantitative determination of the neighbor atomic distance suggests that the degree of short-range order
changes by the temperature altering the second nearest neighbor local atomic configuration of the amorphous when structural
relaxation occurs.
Supported by the Natural Science Foundation of Hebei Province of China (Grant No. A2007000296), the National Natural Science
Foundation of China (Grant No. 50731005), SKPBRC (Grant Nos. 2007CB616915 and 2006CB605201), and PCSIRT (Grant No. IRT0650) 相似文献
234.
235.
用递归法计算了α-Mg与α-Zr的结构能、原子结合能,Mg/Zr界面能与Mg的表面能,Mg中Zr及Zr中Fe,Mn,Si,H等杂质原子相互作用能,Mg,Zr原子态密度及其在合金中的电荷变化. 计算发现,在晶体中与Mg态密度差别很大的Zr在Mg/Zr界面却与Mg趋于相近,从而界面电子环境与Mg相似,为Mg形核生长提供有利条件;α-Zr的结构能、原子结合能低于相应的α-Mg,且Mg/Zr界面能低于Mg的表面能,从能量角度合理解释了Zr先于Mg从Mg熔体析出,并作为异质核心细化Mg晶粒的实验现象. 原子相互作用 相似文献
236.
Agudelo A. C. Marco J. F. Gancedo J. R. Pérez-Alcázar G. A. 《Hyperfine Interactions》2002,139(1-4):141-152
The corrosion reaction of four Fe–Mn–Al alloys exposed to a cycling, dry–humid, SO2 (0.001% by volume) polluted atmosphere was studied. ICEMS, XPS, AES-SAM and transmission Mössbauer spectroscopy at different temperatures were employed to characterize the corrosion products. The analytical results indicate that (i) ferrihydrite is the main component of the rust; (ii) there is an abundant presence of Mn2+ and SO3
2–/SO4
2– on the top of the corrosion layer, the concentration of SO4
2– increasing with the number of cycles; and (iii) the magnetic hyperfine pattern exhibited by the series of low-temperature spectra of the rust is quite different from that observed in the rust formed under similar corrosive environments on iron and weathering steel. This latter finding is correlated with a slow rate of transformation of the Fe3+ species formed at the early stages of corrosion into -FeOOH, the usual final product of this type of corrosion processes. The sulphate anions, abundant inside the electrolyte during the wet periods, could be incorporated to the ferrihydrite structure being responsible for the Mössbauer spectral pattern recorded from the corrosion products at low temperatures. 相似文献
237.
Aït Hmaïdouch L. Mançour Billah S. El Hadek M. Coffy G. 《Journal of Thermal Analysis and Calorimetry》2000,61(1):165-171
The solid-liquid equilibria of the ternary system H2 O-Al(NO3 )3 -Mg(NO3 )2 were studied at 15, 25, 30, 40 and 50°C by using a synthetic method which allows to determine all the characteristic points
of isothermal sections. In all isotherms the liquidus exhibit two curves corresponding to the saturation in Mg(NO3 )2 ⋅6H2 O and Al(NO3 )3 ⋅9H2 O. Neither double salts nor mixed crystals are observed in the temperature and composition field studied.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
238.
Summary X-ray double-crystal rocking curves of Ga1−x
Al
x
As/GaAs heterostructures have been calculated using a dynamical diffraction model for the general case of Bragg reflection
geometry. Different experimental configurations have been considered and the possibility of studying both slightly mismatched
and relatively thin layers has been investigated. Experimental rocking curves have been measured using the CuKα
1 radiation, the 004 symmetric reflection and a perfect crystal as the monochromator. An excellent agreement between calculated
and experimental rocking curves has been found and this demonstrates the reliability of both the experimental procedure and
the theoretical approach. 相似文献
239.
Ca8Mg(SiO4)4Cl2中Ce3+和Eu2+的光谱性质和能量传递 总被引:1,自引:1,他引:0
首次合成了Ce^3+和Eu^2+共激活氯硅酸镁钙Ca8Mg(SiO4)4Cl2:Ce^3+,Eu^2+高效绿色荧光粉,报道了它们的漫反射光谱、激发和发射光,观察到氯硅酸镁钙中Ce^3+ Eu^2+ 相似文献
240.
M.J. Rozenberg 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,2(4):457-461
We propose a novel scenario for the electronic state in the manganese perovskites. We argue that, at low temperatures and
within the ferromagnetic state, the physics of these colossal magnetoresistance compounds may be characterized by a correlated
metallic state near a metal insulator transition where the orbital degrees of freedom play the main role. This follows from
the observation that a two-band degenerate Hubbard model under a strong magnetic field can be mapped onto a para-orbital single
band model. We solve the model numerically using the quantum Monte-Carlo technique within a dynamical mean field theory which
is exact in the limit of large lattice connectivity. We argue that the proposed scenario may allow for the qualitative interpretation
of a variety of experiments which were also observed in other (early) transition metal oxides.
Received: 3 October 1997 / Revised: 9 December 1997 / Accepted: 12 January 1998 相似文献